JPH01106615A - Resonance circuit tuning method and apparatus - Google Patents

Abstract

PURPOSE: To automatically adjust a cloche circuit to be used for a TV receiver and to integrate the cloche circuit by detecting the adjusting state of the cloche circuit by using the amplitude of an excess signal generated from a cliscriminator immediately after the transfer of the cloche circuit from the 1st mode of an excitation circuit to the 2nd mode. CONSTITUTION: Tuning capacitors 2, 3 are connected to a cloche circuit (resonance circuit) to be used for a TV receiver in parallel with an inductor 1. The capacitors 2, 3 constitute a capacitive voltage divider and voltage can be measured without deviating the capacitity of a measuring probe from the range of the cloche circuit. A resistor 5 and an insulating capacitor 6 are connected between an input terminal 7 and the cloche circuit and an output signal is outputted from a terminal 8 connected to the resonance circuit. The excitation mode of the cloche circuit 15 rapidly changed by the resonance circuit, the deviation of a free path is allowed to pass during the conversion of the 1st mode into the 2nd mode and an asynchronized circuit is excited by reference frequency, so that the amplitude can easily be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resonant circuit tuning method and a tuning device. The method and apparatus are used in television circuits, and are used to adjust the tuning of the "Croche A" circuit of a 5ECAF television receiver.

Several methods can be used to adjust this circuit during the manufacture of the television set.

For example, using a device that measures the input current of one resonant circuit and its terminal voltage, it can be determined that the adjustment is correct if these two values are in phase at the reference frequency. These phases are compared on the oscilloscope screen and adjustments are made manually.

However, extremely accurate measurement of phase difference is not easy.
It is difficult to perform automatic adjustment.

As a further alternative to the above method, the signal is formed by a frequency discriminator coupled to the output of the resonant circuit, and the resonant circuit repeats and doubles.
It is possible to successively excite in two different modes and determine the adjustment for tuning the resonant circuit. This kind of method is
The method is disclosed in the German patent application DB-A 2,702,565, in which the signal provided by a frequency discriminator is observed on the screen of an oscilloscope, while the reference frequency of a "crochet" circuit is determined. On the other hand, the resonant circuit is sequentially excited by symmetrically located frequencies, thereby manually adjusting the resonant circuit.

The object of the invention is to realize a method which is more accurate and easier to automate, and which can therefore be integrated into any kind of television receiver (set), in which a decrochet circuit is implemented within the television set itself. The object of the present invention is to obtain a device that allows automatic adjustment.

A device of this type is particularly advantageous when the crochet J circuit is constructed from a switched capacitor integrated circuit.

The method according to the invention therefore uses the amplitude of the transient signal produced by the discriminator immediately after the changeover from the first mode to the second mode of the excitation circuit to detect the regulation state, and for each iteration the circuit is first It is characterized in that it is excited with a signal having a frequency of the fundamental tuning frequency.

This method requires the provision of only one single frequency, and a signal whose amplitude is easily measured can be used to determine the adjustment value.

A very simple variant is to rapidly suppress the repetitive signal at a predetermined instant during each iteration.

In yet another variation, improved sensitivity is obtained by rapidly rotating the phase of the repetition signal by 180°, at least once during each repetition period.

The generated signal of the discriminator is also sampled at two instants, one instant corresponding to the speed fixed by the excitation at the reference frequency, and the other instant corresponding to the change from the first mode to the second mode. It is possible to eliminate the effects of misadjustment of the frequency discriminator by allowing it to occur immediately after the transition and using the difference between these two samples to determine the adjustment.

A resonant circuit tuning device, which is used, for example, in a decoder stage of a SECAM television set, and which has a tuneable resonant circuit and at least one frequency discriminator coupled to the output of the resonant circuit, resonates at a desired reference frequency. a signal generator for generating a signal for the circuit and causing a rapid change at a first instant; a synchronizer for detecting said first instant as well as a second instant immediately following this first instant; a device for displacing the signal supplied by the signal generator to the resonant circuit during the time period including the instant; and a device for sampling the signal supplied by the discriminator at the second instant, shaping this sample signal, A device for providing an error signal that is a function of the amplitude of the signal, and a device for adjusting the resonant circuit as a function of the error signal.

The synchronization effect allows the first instant to be displayed once during each field retrace period.

The device according to the invention has the advantage that it is possible to economize the control stage of the resonant circuit used during the manufacture of the television set, and furthermore that the control function of this circuit can be fully maintained over the entire life of the television set. has.

The signal generator consists of an oscillator whose frequency is controlled by a feedback loop based on the line frequency, which makes it possible to obtain economical and complete stability.

The resonant circuit adjustment device has means for controlling the switching of the capacitors, the control means comprising a memory, the contents of which are changed during each sample operation depending on the polarity sign of the signal supplied by the discriminator. The signal is slightly increased (incremented) or slightly decreased (decremented), and when the absolute value of the signal is less than a predetermined value, it is maintained as it is, and the contents of the memory are represented by double codes, and each of these Advantageously, the bit controls one switch of the capacitor.

misfortune The present invention will be explained below with reference to the drawings.

The r-crochet circuit shown in FIG. 1 is currently used in the manufacture of television sets. This circuit has a conventional resonant circuit constructed by placing tuning capacitors 2 and 3 in parallel with an inductance 1.

There are two capacitors 2, 3 in the circuit, forming a capacitive voltage divider, which allows the voltage to be measured without fear of the capacitance of the measuring probe being outside the range of the circuit.

A resistor 5 and an insulating capacitor 6 are placed between the input cuff and the main circuit. An output signal is produced at terminal 8, which is connected to the resonant circuit. Furthermore, capacitor 4 is provided only for electrical insulation.

Further, in this circuit, the capacitor 3 can be omitted when there is no need to measure the voltage level of the circuit itself.

The principle of the method of the invention is to rapidly change the excitation mode of the circuit, and during the conversion from the first mode to the second mode, the circuit passes through a "free path" transition phase, and this In phase, the actual property is that for a short instant, an out-of-tune circuit (i.e., when the actual frequency deviates from the reference frequency) is excited at the reference frequency, and there is a discontinuity in the mode being excited. In some cases, the oscillation frequency before the discontinuity is clearly the reference frequency, and this is also the case when the discontinuity is followed by a period of time. However, between the two instants the circuit produces a specific reaction depending on its natural frequency and the overvoltage.

FIGS. 2 and 3 are for explaining this phenomenon. These figures were created by computer simulation of a resonant circuit having an overvoltage value of 16 (16 times) with respect to the overvoltage of the r-crochet J4 circuit. At the base point of the horizontal axis, the excitation voltage is suddenly increased to 18
Shift by 0°. In other words, the signal is inverted. In FIG. 2, excitation is performed at a tuned frequency, and in FIG. 3, excitation is performed at a frequency 0.99 times the natural frequency of the circuit.

In the first case shown in FIG. 2, the phase width amplitude of the "free path" decreases, cancels out, and then increases again to the initial level. Since the initial frequency is the natural frequency of the circuit, if there is no change in the excitation mode of the circuit, the zero crossings of the output wave are regular and occur at the same instant, and there is no reason to change this.

In the second case shown in FIG. 3, the amplitude is reduced but not canceled.

The frequency tends to shift in a direction corresponding to either the positive or negative polarity sign of the difference between the excitation frequency and the natural frequency. That is, in this case there is a tendency to increase and the zero crossing occurs earlier than in the previous case. Eventually the ly2 period is lost and the signal is again in phase with the new excitation voltage. This frequency is still 0.99 times the actual frequency as before.

Since the frequency changes and the amplitude is not equal to zero, 1907
The frequency discriminator coupled to the output of the 911 circuit is the fourth
A signal with a waveform as shown in the figure is generated. In the case of FIG. 2, this frequency discriminator is assumed to be controlled symmetrically with respect to the reference frequency, so it does not produce any signal.

Of course, if the starting frequency is higher than the circuit frequency, the transient drift will occur in the opposite direction, and the resulting signal at the discriminator will also be of opposite polarity. In this case, this signal helps determine which direction of movement is required to achieve circuit tuning.

FIG. 5 is a diagram illustrating the sensitivity obtained by the above method. In FIG. 4, the pulse amplitude (■...volt) is plotted on the vertical axis, and the out-of-tuning frequency (kHz) is plotted on the horizontal axis. This curve was obtained by varying the excitation signal stepwise and measuring the peak voltage of each pulse.

As seen from this curve, the maximum amplitude is 6 to 8 kllz
Already reached at a frequency deviation of . On the other hand, the normally allowed adjustment deviation for a crochet circuit is about 40 kt (z). Therefore, the method obtains a very exceptionally advantageous sensitivity.
A frequency variation was measured that transiently provided the output of the frequency discriminator with the same amplitude as for a permanent deviation of 0 kHz. This means increasing the sensitivity to 80/1 (80 times).

Changes in the excitation behavior are made iteratively so that the resulting effect can be measured. In the check and/or adjustment circuit of the "r crochet" circuit, the 4.286 MHz wave is
07911 circuit which causes this wave to cause a 180° phase jump once during each scan line of the television image. In some types of television sets, the signal provided by the discriminator is
Only the two lines have different DC levels and different signs (polarity). The effect obtained therefore only needs to be measured during one of the two lines. Although it is not useful for automating adjustments, it is interesting to observe the visible effect on the screen of the television set, which can be used for manual adjustments. Perfect synchronization results in a uniform magenta shadow on the screen. When out of phase, a vertical bar appears corresponding to the out of phase, which appears blue or red depending on the direction of the out of alignment. This process is extremely sensitive, and bars of this type occur long before the conventional standards are out of alignment. A predetermined tolerance range (e.g. 4.286MHz
The two limit frequencies (here 4
．． 246 and 4.326MH2) on several lines,
Each of these frequencies causes a phase break at a different line instant. If the circuit is within tolerance, there will be two bars of different colors on the screen; if the circuit is outside this range, there will be two bands of the same color. (Red or blue bars result depending on the direction of out-of-adjustment).

Instead of inverting the signal, it is also possible to suppress the signal rapidly. During the phase in which the signal in the circuit is attenuated and reduced, the frequency slides towards the reference value, and this sliding occurs before the signal cancels out. An alternative is to suppress the signal only during a time window and then restore the signal to its initial phase. This results in successive slides in opposite directions. In any case, a phase jump of 180'' results in a device with extremely high intensity and in which the signal supplied by the discriminator can be used more flexibly.

In the automatic adjustment device for resonant circuits shown in FIG. 6, an oscillator 9 followed by an inverter 11 feeds a resonant circuit 16, which is followed by a frequency discriminator 15. If the resonant circuit 16 is an r-crochet circuit other than a SECAM decoder unit, the discriminator 15 is incorporated as part of the television set. A synchronization signal source lO provides line and field signals and color identification signals to a synchronization signal and window generator 12. This generator supplies a signal to an inverter 11, which produces a 180" phase jump. Said generator 12 also supplies a measurement and process circuit 13, the two time windows of which It is used to measure transient signals.The measurement results of the measurement circuit 13 are
4. For adjustment devices used in factories, this element is a chain of drive circuits that mechanically adjusts the resonant circuit 16. In a regulating device incorporated in a television set having a "crochet" circuit with a switching capacitor network switched by an integrated inclination converter, the element 14 is an electronic logic circuit, whereby the electronic The opening and closing of the interrupter is controlled, and a specific capacitor of the filter is activated or deactivated.

This element of the device described above can be readily configured by a person skilled in the art to have the following functions for a factory adjustment device.

Oscillator 9: This oscillator can be configured as a crystal oscillator, for example, and its oscillation frequency can be twice the reference frequency, that is, 8.572 MHz.

Inverter 11: This inverter is a bistable trigger circuit that divides the 8.572 MHz signal into two, producing two opposite polarities in its two outputs. Each of these outputs is connected through a gate to the r-crochet J circuit described above so that only one of the two gates is opened at each time. The synchronization signal and the signal generated by window generator 12 change the state of the gate. Alternatively, the bistable trigger circuit that divides the oscillating signal into two may inhibit its operation for one period when receiving the signal from the peak generator 12, ie causing a 180 DEG phase jump in the output signal. The signal mentioned above is a square wave signal, and the waveform is not important. This is because the harmonics are filtered by this resonant circuit. A changeover switch 17 is provided at the output, the purpose of which is to supply a signal only during the forward phase of line scanning. During the retrace period, a synchronization signal and a general identification burst are provided by a synchronization signal source 10, which signals may optionally be derived from an already provided test pattern generator.

Window generator 12: This window generator generates different signals based on the line synchronization signal.

This generator supplies a synchronization signal to the inverter 11, for example approximately 15 μs after the start of the line. This generator supplies the measuring circuit 13 with a measuring window that starts approximately 1 μs after the synchronization signal and has a length of approximately 3 μs, and also a second window of the same length, e.g. It is generated 10 to 20 μs after. These windows occur only between one of the two lines, and during a given line type (red or blue). This selection is controlled by a color identification signal generated by generator 10. This latter generator 10 supplies the control window of the changeover switch 17 to the output of the inverter. Circuits for generating these signals, especially circuits based on the principle of successively dividing the clock signal and the line synchronization signal, can easily realize this.

Measuring circuit 13: The transient signal generated by the discriminator 15 can have variable polarity and variable amplitude depending on the discriminator adjustment, circuit characteristics, line type (blue/red). child,
To eliminate these shadows, generator 12 provides a measurement window only between predetermined lines as described above.

Furthermore, this signal is superimposed on the DC signal, and the magnitude of this DC signal is also determined by the same parameter. The two consecutive windows described above for generator 12 are used to eliminate the effects of DC signals. The values provided by the discriminator are accumulated between these two windows, and (
(For example, a capacitor is charged to a value corresponding to this value and stored in an analog manner.) Also, this storage is performed for each separate capacitor, and then the difference between these two values is detected by a generating circuit, and the above-mentioned element 14 and adjust accordingly. In the case of the SRCAM decoder shown in FIG.
1 circuit 16 is provided, in which case the invention is particularly advantageous, since a discriminator is already provided and a synchronization signal source is already integrated as part of the television set. So these circuits can be used. In this case, the following elements are used.

The television set's synchronization signal source provides line and field synchronization signals at inputs 32 and 33, respectively.

The elements designated by reference numerals 19-31 are elements of a known and conventionally used decoder unit.

A composite video signal that is processed within a dedicated portion of the television set (not shown) is provided through an input terminal 34. Furthermore, through the capacitor and the incluctor switch 117 whose mission will be described later,
Further, via the r-crochet 1 circuit 16, this composite signal is fed to a limiting amplifier 31, at the output of which this signal is switched in two directions. One direction leads directly to the passage of the rectifier 23. In the opposite direction, there are other paths, ie, an impedance matching circuit 19, a delay line 20, another matching circuit 21, and a compensation amplifier 2.
This leads to the second circuit. Each output of the rectifier circuit 23 includes a limiter 24, a frequency discriminator 25, and a de-emphasis.
A cascade arrangement of circuit 26 and output stage 27 is provided.

The signal is also fed to an output 30, which output is connected to an identification circuit 29 which drives a bistable circuit 28 which is triggered by the line synchronization signal at 32 and is switched The circuit 23 is controlled.

All of these parts are known and are shown and described herein to provide an understanding of how the circuit elements 110-117 according to the present invention may be connected thereto.

Furthermore, circuit arrangements different from those shown in the drawings can also be used. These circuit arrangements have the same signal inputs, discriminator outputs and synchronization signals, and it is clear that the invention may be applied in the same way.

During each field retrace over one or several lines, the field synchronization signal at terminal 33 is used to trigger the adjustment process. Alternatively, it is possible to start such a process each time the television set is put into operation.

However, it is easier not to perform special operations when starting up the television set, and furthermore, since the drift of the filter becomes large after the set is put into operation, it is more convenient to make adjustments for each field.

In television sets with at least partially digitized circuitry, the signal generator 111 can be constructed on the basis of an internal clock present in the television set. Known phase-locked loop circuits generate frequencies that are multiples of the line frequency fL. When multiplied by 274, this frequency is 4.28125
MHz, which is only 4.7 MHz compared to the desired frequency.
It is only 5 kHz less. Since the conventionally generally accepted deviation is 40 kHz, the sensitivity of this method using 274X fL is extremely high. However, if higher precision is required, 1646
By generating a frequency of , and then dividing this frequency into six (first by dividing into three, then by dividing into two to obtain a cycle ratio l), the error becomes less than 500 Hz. or 27
Generate 43x fL, divide it into 5 parts, then divide it into 2 parts.
To divide. (The error is 62.5 Hz.) This signal generator 111 further has an in and a bark similar to the inverter 11 described above, and inserts a phase change during line feedback. The flip-flop of this inverter generates the final frequency to be divided by two.

Synchronizer 112 generates a control signal, which control signal is 1
It has a period equal to the line period or a fraction of the line period, which occurs during field retrace, and provides this control signal to the changeover switches 110,117.

This changeover switch has the function of replacing the signal at terminal 34 with the signal supplied by signal generator 111 during the period of this control signal. (This changeover switch is naturally an electronic switch.) This control signal is triggered by the field retrace synchronization signal. The output of the bistable circuit 28 controlling the switching device is also fed to a synchronizer 112, which allows the same colored lines to be selected during each field retrace.

At a first instant during this line period, a synchronization signal is supplied to the signal generator 111 through the synchronizer 112;
This causes the signal generator 111 to be triggered to produce a rapid change, in particular a 180° phase change by inverting the signal. Finally, the signal generator 112 supplies the sample and process circuit 113 approximately 1 μs after this first instant, providing it with a measurement window having a time length of approximately 3 μs. Then after the aforementioned second instant 10-20
A second window of the same length of time is provided at a third instant occurring after μs. (These devices are for making adjustments during the manufacturing process). The second instant occurs rapidly after the first instant and during this time the resonant circuit is
a period corresponding to a "free path" occurs, the third instant corresponds to a fixed speed, i.e. it occurs before the two first instants, or after a sufficient time has elapsed after these two instants; Allow the resonant circuit to return to a stable excitation state.

The above-mentioned sample circuit 113 is connected to the output of the frequency discriminator 26 and performs the same function as the frequency discriminator 13 shown in FIG. In any case, the presence of two storage capacitors with analog values poses difficulties when implementing the device in an integrated circuit. In such a case, two analog-to-digital converters are used. The construction of these converters is extremely simple. The reason is that when the desired adjustment accuracy is obtained, the amplitude of the transient pulse is still quite large, and this value is sufficient for a rough comparison of the two sample values divided between the two windows. This is because. In such a case the converter can be constructed as having only a few bits.

Furthermore, since the duration of the transient pulse is on the order of a few microseconds, the operation need not be extremely rapid. These transducers (specifying a small number of unique thresholds,
and constructing a circuit by comparing the signal with each of these thresholds by several comparators, or by one comparator switching its reference input to each of these thresholds in turn and comparing. Can be done. The comparator corresponding to at least the first time window is followed by a latch circuit to maintain its sample value until the second time window or to compare these two samples.

"The crochet 1 circuit 16 has a predetermined number of switched capacitors 116. It is possible to select a sufficiently high value for the inductance and reduce the value of the capacitor,
These capacitors can be integrated with changeover switches. With a total capacitance of approximately 160 pF and an adjustable amplitude of 10%, the total value of switch capacitor 116 will be approximately 15 pF. These can be divided, for example, into four units, each with a pFO value of 1.2.4.8, so that the total capacitance can be adjusted in frequency with an accuracy of 1 pF, or an accuracy of 0.6%. , 0.3% accuracy or approximately 13kHz accuracy.

The control circuit 114 of the electronic shut-off circuit can be constructed with up to 16 counts, ie, a 4-bit up-down counter. This up-down counter is set to 1 by the polarity of the voltage obtained by the comparison between the two samples obtained by the output of the discriminator for each field retrace.
Increments or decrements one unit at a time. However, the absolute value of this voltage is the limit value allowed by the adjustment accuracy, e.g.
If it is below kHz, the above-mentioned counter is not activated. The counter retains its count value like a memory unless it is driven. Therefore, in such a case, each of the switched capacitors 116 can be individually controlled by a bit from the counter to effect the correct adjustment of the frequency of the "crochet" circuit after several fields. It is natural that the highest value capacitor should be connected to the most significant bit, and so on.

It will be appreciated that each of the elements described above may be readily constructed by one skilled in the basic logic circuit arts, and may be readily integrated onto a monolithic circuit.

In addition to the above, the method of the present invention has transient characteristics of r crochet 1.
It can be used to tune any filter circuit similar to the circuit, ie at least it can be adapted for filters with synchronous sidebands. For embedded devices with periodic operation any type of filter can be used, which is applicable in all cases where the useful signal can be replaced by a specific regulation signal.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a resonant circuit called ``Croche 1 circuit'' of a SECAM television set; Fig. 2.3.4 is a diagram showing waveforms corresponding to the time of each signal generated in this device; FIG. 5 is a diagram showing the sensitivity when using the invention; FIG. 6 is a block diagram of an apparatus using the invention during the manufacturing process; FIG. It is a block diagram in which a part shown in FIG.
Measurement and process circuit 14...Measurement and process elements 15, 25...Frequency discriminator 16...Resonance circuit (r crochet j circuit) 19, 21
... Matching circuit 20 ... Delay line 23 ... Exchange circuit 24 ... Limiter 26 ... De-emphasis circuit 28 ... Bistable circuit 111 ... Signal generator 112 ... Synchronization circuit 114 ...Control circuit patent applicant N.B.Philips Fluiranpenfabriken, patent attorney Akira Sugimura, patent attorney Sugi
Written by Ko Mura

Claims (1)

[Claims] 1. Using a signal generated by a frequency discriminator coupled to the output of a resonant circuit, the resonant circuit is
and a resonant circuit tuning method that detects and adjusts the tuning of a resonant circuit by repeatedly and continuously exciting the circuit in a second mode, wherein the discrimination is performed immediately after switching between the first mode and the second mode of exciting the circuit. 1. A method for tuning a resonant circuit, characterized in that the amplitude of a transient signal produced by a resonant circuit is used to detect the tuning state, and in each iteration the resonant circuit is first excited with a signal having a reference tuning frequency. 2. The method of claim 1, further comprising rapidly suppressing the repetitive signal at a predetermined instant during each iteration. 3. The method of claim 1, further comprising rapidly reversing the phase of the repetitive signal by 180° at least once during each repetition period. 4. Sample the signal produced by the frequency discriminator at two instants, one of which corresponds to the ratio determined by the excitation at the reference frequency, and the other immediately after the transition from the first mode to the second mode. 4. A method as claimed in claim 1, 2 or 3, characterized in that the difference between the two samples results in a signal determining the adjustment. 5. In a resonant circuit tuning device having a tunable resonant circuit and at least one frequency discriminator coupled to the output of the resonant circuit, generating a signal feeding the resonant circuit at a desired reference frequency and at a first instant of time a signal generator for causing a rapid change; a synchronizer for detecting said first instant as well as a second instant immediately subsequent to said first instant; said signal generating during a time period including said first instant; a device for displacing the signal supplied by the discriminator to the resonant circuit at a second instant, and shaping the sampled signal to provide an error signal that is a function of the amplitude of the sampled signal. and a device for adjusting the resonant circuit as a function of an error signal. 6. The generator has a circuit stage with two outputs, supplying these two outputs with signals of opposite phase, and furthermore the generator has a changeover switch for switching the output from which the signal is derived at the first instant. 6. The device according to claim 5, characterized in that it comprises: 7. The device according to claim 5, characterized in that the signal generator is constituted by an oscillator whose phase is controlled by a phase-locked loop based on the line frequency. 8. The synchronizer further determines a third instant corresponding to a fixed excitation speed at the reference frequency, and the apparatus has a device for sampling the signal provided by the discriminator at the third instant, and further includes an error signal supply. 8. Device according to claim 5, 6 or 7, characterized in that the device comprises a comparator for deriving the difference between the amplitude of the signal at the second instant and the amplitude of the signal at the third instant. 9. The resonant circuit adjustment device has means for controlling switching of the capacitor, the control means comprising a memory,
Its content is slightly increased or decreased depending on the polarity sign of the signal supplied by the discriminator during each sample operation, or remains unchanged if the absolute value of the signal is less than a predetermined value. 9. Device according to any one of claims 5 to 8, wherein the memory is maintained in a state and the contents of the memory are represented by a binary code, each bit of which controls a switch of one of the capacitors. 10. Apparatus according to any one of claims 5 to 9, wherein the synchronizer displays the first instant once during each field retrace period.